Ozone is an oxidizing agent which finds use in the treatment of, for example, water to produce a potable product.
It is known to produce ozone from an ozonizer using an oxygen rich feed gas which has been produced from a pressure swing adsorption (PSA) plant. Use of an oxygen rich gas produced by PSA techniques is very attractive for the generation of ozone in as much as it contains 8% of nitrogen and argon with substantially no water vapor which increases the efficiency of the ozone generator. When oxygen rich PSA gas is used as the feed gas for an ozonizer the maximum concentration of ozone that can be achieved is normally less than 10% but often the ozonizer is set to produce ozone at a concentration by volume of 5%.
Although, when compared to the use of air as a feed gas for the ozonizer, the ozonizer is decreased in size for the same output of ozone, the remainder of the oxygen rich gas which has not been converted to ozone is sometimes wasted, used in a different part of a subsequent process or needs to be cleaned up and returned to the process.
Japanese Published Patent Application 52081092 discloses a method of and apparatus for the production of ozone. Feed air is passed through a pressure vessel forming part of a PSA plant in which is located an adsorbent bed which preferentially adsorbs nitrogen. The oxygen rich gas leaving the pressure vessel is then delivered to an ozonizer where is undergoes silent discharge at a high voltage such that a portion of the oxygen is ozonized. The ozonized oxygen then leaves the ozonizer and is introduced into a separate low temperature ozone adsorber where the ozone is separated by being adsorbed while the oxygen leaves the ozone adsorber and can be recycled by means of a blower to blend with the oxygen leaving the pressure vessel before entry into the ozonizer.
The nitrogen generated in the pressure vessel is fed directly to the low temperature ozone adsorber where it desorbs the ozone and is discharged in the form of a ozone/nitrogen feed gas for passage to a material to be treated.
A disadvantage of the apparatus described in Japanese Published Patent Application 52081092 is that the recycled oxygen rich gas requires recompression before it can be used again. Further, the apparatus requires the provision of a separate low temperature ozone adsorber.